How about Moana? It's pronounced mo-ah-na not moan-a, and means ocean in Hawaiian and Maori. Or maybe Belen, Astra, Sela, Xenia, or Waverly? And I know somebody already suggested Junia, but I think that would be so perfect with your other children's names! Good luck, I'm sure you'll find something just right sooner or later

I second the notion of considering Zinnia again! I think you were mentioning the troubles with your son with the 'Z' name, and having two Z names might lesson his 'everyone else has a recognizable name' issue....maybe? At least he and she could be name-buddies, in a way I actually have five kids too, and the more kids I had, the more creative I wanted their names to be (I guess because I was hanging out with more and more kids!!). Well, when it came time for number 5,I knew my husband had pined for all the previous years for a girl name Katie/Kate but had all but given up (I like that name but it is horrible with our last name (also starts with a K) and it seemed so common and just a bit boring to me). Then I stumbled across Katriel, and loved it, and yay -he could still call her Kate/Katie (which he does)! Double win! But my word, NO ONE can pronounce this name, or remember it, or even say it how we say it - Kay-tree-el. I thought it was phonetic! And of course everyone can pronounce, say, spell every one of my other kids' names...so, your post spoke to me on a lot of levels
On your list so far I love Saffron, but when I say your son's name with a Z, it sounds very similar to this, although I may be saying them both wrong! I, too, love the nn Fia, and my personal favorite is just Fia! I was really hoping Nova or Roxanne would work out, because they seem to have the same vibe as your other kids' names, and I love them both.
Ok - so new names to suggest. Oona! I know one little girl with this name, (her sister's name is Mary), and for some reason the bounce yet elegance of it really get me.
Other ideas:
SabrynnShireAdair
MielleMatteaVesperRoseRayneTovaToscaMilla (I like Rosemilla too, as one name)RavennaRaquel

That's all I could come up with....Good Luck! (PS - my sister's son's middle name is Rook! Everyone loves it!)

Neroli is pronounced basically like Merrily but with an N - but I can totally see where you'd struggle a bit! My family all seem to have slightly uncommon names - my grandmother is Neroli, I'm Jemima, my twin sister is Gretel, my brother is Barnaby....!
WDYT of Fern? I just LOVE the Charlotte's Web reference, and I think it has such a lovely fresh feel to it. Other options (sorry, I'm starting to get a bit obsessed!):Calla (Callie)LarkClover (I love the character from What Katy Did... is "Cloey" (prn Chloe) too much of a stretch for a nn do you think?)Fleur (I have to say, Fleur Delacour did make this one wearable for me!)DaphneTulip (too far out?)CoralCornelia (nn Nellie?)Clementine (I personally love this... nn Cleo)
CelandineMay (the mayflower is so pretty! I know a two-year-old May who is the cutest little girl)HeatherScarlettRowanMarigold (too far out again? The nn Marie if you wanted to tone it down, or Goldie if you wanted to play it up! And marigolds are so pretty)
Sorry, I got a bit carried away... I totally used this as an excuse to go through my comprehensive Flower Fairies book. And the LilacFairy made me love LilacEVEN MORE! 228864.jpg
Best of luck!